Cornea

Question 1

Corneal edema

Epithelial

• basal epi cell degenerative changes
• development of extra-epi cellular
  fluid filled spaces

Causes

• response to insult
• disturbance of pump function (intraocular fluid accumulation pressure = corneal swelling pressure)
• secondary to outside factors - mechanical, chem, radiation - that disrupt barrier effect of epi and lets fluid in
• ABs can cause => medicamentosa
• CLs
• Epi defects
• Swimming
• Glaucoma: angle closure, high pressure open angle

Symptoms/Findings

• Variable Sxs
• Epithelial Microcysts: small,round, refractile
  
  • Origin: basal epi migrate to surface
• Cysts => hurt if big
• Bullae: flat, pebble-like
  
  • Form when excess fluid accum in corneal epi => epi sep from BM
  • Painful; @ subepi
• Later will see interepithelial and subepithelial pockets of fluid
• Bowmans is intact
• Grey surface, loss of luster, hazy
• PMMA overwear: central circular clouding (sclerotic scatter)
• Decreased VA, glare, halos, fog
• Distorted corneal reflex
• Halo if epi defect
• Rough epi, loss of transparency if swimming, medication

Answer 1

Treatment

• Remove cause
• Non-preserved carboxymethlycellulose
• Hypertonic drops => NaCl aids transition of fluid from epi by drawing water out
  
  • 0.9% osmolarity
  • Glycerin clears epi in severe cases, temporary
• Increased evaporation (fan,hairdryer)
• Pt ed gets better as day goes on
• Bandaged CL => relieves bullae pain
• Poor vision => Anterior stromal cautery scars to form firm
  adhesion btwn epi and stroma
• Amniotic membrane
• Excimer laser
• Collagen cross-linking => riboflavin, UVA

Misc

• Clinical Hx impt in Dx
• Age of onset
• Duration of Sx
• Uni or bilat
• FHx
• Ocular medications
• Prev ocular disease, surgery
• Diurnal variation
• Environmental efx on sxs

Question 2

Corneal edema

Stromal

• Distorted fibrillar distributions
• lakes where fibrils are missing => large change in n
• thicker stroma => pachymetry to measure
• interference with endo pump or barrier function

Causes

• hypoxia
• soft CL
• Fuch’s distrophy - elderly
• Surgical/trauma
• Endo dysfx
• Infections (corneal ulcers, endophthalmitis)
• IO inflamm (keratic precipitates)
• Descemet’s rupture
• Long standing increased IOP (open angle glaucoma)
• Toxic substances in AC

Symptoms/Findings

• painless
• cloudy thickening of stroma
• mild VA reduction
• mild glare
• Folds @ Descemet’s(>10% thickness)
• specular microscopy to determine density and morphology
• striae (>5% thickness)
• generally minimal Sxs until advanced

Answer 2

Treatment

• difficult
• treat underlying causes
• lower IOP ʹ helps pumps
  
  • IOP > swelling pressure = epi edema
  • Endo fx compromised, can happen IOP =30
• steroids if inflamm origin
• increase endo tight junctions temp
• Descemet’s Stripping & Automatic Endothelial
  Keratoplasty (DSAEK) => remove bad Descemet’s and
  endo, replace with donor, balloon

Misc

• Leads to epithelial edema secondary to buckling epithelium
• Hypoxia => lactate => increase osm pressure => edema
• Normal corneal thickness = 540 - 550

Question 3

Corneal scarring

• Stages of Wound Healing:
  
  • Transparent keratocytes => migratory
    fibroblasts => wound margin
  • Fibroblasts => non-motile, contractile
    myofibroblasts
  • Wound closure = myofibroblasts disappear

Answer 3

Appearance:

• White due to new collagen being different from old collagen
• Not transparent

Treatments:

• Most don’t need- only if large or in visual axis
• Treatment is phototherapeutic keratectomy (PTK) if in superficial 50-75 microns
• Superficial Anterior Lamellar Keratoplasty (SALK) if in anterior third

Question 4

Corneal Neovascularization

• Normal Capillaries: 1- 2mm beyond limbus
• Anything beyond is neovasc
• Ghost vessels: not perfused
• Down VA if in axis

Answer 4

Causes:

• Tight soft CLs
• Trachoma
• Superior limbal keratitis
• Anoxia
• Hypoxia
• Interstitial keratitis => neo in stroma
  
  • 90% secondary to congenital syphilis
  • Other systemic diseases: TB, mumps Infectious neo deep in stroma

Question 5

Corneal injury

Sources

• Infections (bacterial, viral, fungal)
• Foreign Bodies
• CL over/wear
• Burn (heat, radiation, chem)
• Secondary to trauma

Sxs

• Pain, discomfort
• Halos => colour
  
  • Diffraction of light d/t epi edema, tearing
• Normal ʹ impaired VA (depends on location,severity)
  
  • Loss of central transparency
  • Increased tearing =>water leak into wound
• Photophobia
  
  • Inflamm iris, CB spasm
• Excessive lacrimation (can cause edema)

Answer 5

Treatment

• Mostly involve epithelium
  
  • Supepi and stromal plexus
• Painful bc high [nerves], CN V1

Pressure Patch

• Area > 10mm2
• NEVER with CL, organic cause
• RTC 24 hours

Seidel Sign

• See if aq fluid leaking out
• • Sidel: clear aq in FL stain

Abrasion

• removal of epithelial cells => FL pool
  
  • Sharp edges
  • If deep, FL => stroma
• Negative staining => irregular epi grows back raised
  
  • Prone to recurrent erosion
• No FB before treatment
• Check C&F before dyes
• Topical ABs
  
  • Gtts: polytrim, vigamox, tobrex, ciloxan ʹ QID or q4h
  • Ung: polysporin, tobramycin BID or QID
  • Recurrent: ung hs 1 month
• Cycloplegic for iritis: cyclopentalate BID,homatropine,
• NSAIDs gtts: Acular, Levro nepafenac TID
• RTC 24 hours => 2-3 days (dilute)

Healing

• Adj cells slide over
  
  • chem burn = conj cells from Palisades of Vogt
• Fibronectin = glue to hold cells together
• Mitosis w/in 24 hrs (basal, amplying, stem cells)
• Smoother = heals faster
• BM = 6-8wk regen
  
  • epi can only adhere to bowmans via BM

Question 6

Recurrent Corneal Erosion

• History of injury (organic,fingernail, EBMD)
• Negative staining
• Punctal plugs is option

Answer 6

Treatment

• Gtts day, ung hs until healed; pressure patch
• Debridement
• Bandage CL (3mo)
• Anterior stromal puncture (25-27 gauge needle => bowmans => stim secure binding of epi)
• Photo Therapeutic Keratectomy
• Muro 128 ung, FreshKote ATs TID, Loteprednol
  (QID/2wks Æ BID/6wks; IOP check day 3), Doxycycline
  BID (can reduce MMP activity and prevent further
  episodes)

Question 7

Abrasion vs Ulcer

Answer 7

• Hx: trauma
• doesnt go beyond bowmans
• none/small infiltrate
• FL stay in wound, small halo
• Small edema
• Heaped up epi
• Localized redness
• no discharge

Question 8

Foreign body treatment

Answer 8

• Irrigate
• Cotton swap
• Spud, 25 gauge needle
• Alger brush
  
  • Stops at Bowmans
• Flip lids and ensure nothing embedded under upper lid
• Once out, treat like abrasion

Question 9

Ulcer

• Inflamm mediated breakdown of stromal matrix,
  thinning
• Corneal: loss of superficial tissue,result of infection,
  inflamm that lead to necrosis
  
  • Disruption of epi layer w stomal involvement

Answer 9

Presentation

• Pain, no trauma
• Beyond bowmans
• Infiltrate (WBC) in stroma (white) that takes up FL and diffuses in stroma
• marked epi and stromal edema
• red, angry eye
• purulent discharge
• circumlimbal flushed
• AC rxn
• Lose corneal sensitivity
• Infected abrasion => ulcer
• Occur secondary to unattended epi defect
• Bacteria: nisseria
• Enzymatic destruction of macromolecules that make
  up collagen
• Uclers can be sight threatening
• Treatment is complicated
• Hx: pain, no trauma
• Beyond bowmans
• Surrounded by infiltrate
• Ulcer takes up FL, diffuse to stroma
• Marked epi/stromal edema
• Red angry eye
• Purulent discharge
• Circumlimbal flush
• Marked AC rxn